Aug. 10, 2015 – As fall calving season nears, attention shifts to the cow’s reproductive tract and fetus. Located at the Animal Science Image Gallery are ten pictures of cow pregnancies from 30 days to 4.5 months of gestation.
Once at the page, type 3549 into the search bar to view the images. These images are from Dr. T. Y. Tanabe’s research with pregnant cows between 1949 and 1954, mostly at Pennsylvania State University.
Labeling for the images are as follows: C = cotyledon, CL = corpus luteum, Em = embryo, Ov = ovary, S = Serosa.
In Image 1, the reproductive tract was opened to reveal an 11-mm embryo at about 30 days of gestation, well before complete attachment of the extra-embryonic membranes to the uterus. Although it is not clearly visible, the serosa extra-embryonic membrane fills the pregnant horn, and has begun to grow into the other horn.
The 18-mm embryo in image 2 was removed from the uterus within the amnion. Based on its length, it was at about 36 days of gestation.
At 45 days post-insemination, image 3 shows a 29-mm embryo at the end of the period of the embryo (and the beginning of the period of the fetus) when the extra-embryonic membranes have firmly attached to the uterus to form the placenta. The chorion extends nearly the full length of the non-gravid uterine horn.
In image 4, a window was cut through the wall of the uterus to reveal a 32-mm conceptus (1.5 months of gestation) in the amnion early in the period of the fetus.
Image 5 similarly reveals an 87-mm fetus at 66 days of gestation.
Image 6 shows a 95-mm fetus in the amnion, estimated at 72 days of gestation.
In image 7, the fetus (13.3cm at 84 days of gestation) was removed from the uterus surrounded by the amnion and the chorion. Floating in saline, numerous villi are evident on the chorionic cotyledons. These villi protrude into crypts in the uterine cotyledons (sometimes called caruncles) to form the placenta.
In image 8, the extra-embryonic membranes were removed to reveal a 15-cm fetus (estimated at 95 days of gestation).
The crypts in the uterine cotyledons evident image 9 accommodate villi (see image 7) from chorionic cotyledons to form the placenta.
The uterus in image 10 was from a cow at 4.5 months of pregnancy. To check out all 10 images, visit Animal Science Image Gallery and search for file/images 3549.